Candida albicans is the most prevalent human fungal pathogen and is capable of causing invasive candidiasis, a severe disease with high mortality rates and medical costs. Fluconazole is the most frequently prescribed oral antifungal for treating Candida infections and acquired resistance to fluconazole (FluR) is a significant problem. Aneuploidies, which arise from non-disjunction events that involve centromeres, are strongly correlated with FluR. C. albicans centromeres are unique in being regional, like those of higher eukaryotes, yet attaching to a single microtubule and lacking pericentric heterochromatin, like Saccharomyces cerevisiae point centromeres. Characterization of C. albicans centromeres and the kinetochore protein components associated with them will provide a better understanding of CEN structure and function. This knowledge can be exploited for the identification of direct anti-fungal drugs as well as for the development of companion drugs that alter the frequency of aneuploidies and the acquisition of FluR,by altering CEN function. This project will characterize the structure of the C. albicans kinetochore, focusing on members of the DASH protein complex. Predicted homologs of DASH complex members in S. cerevisiae and Schizosaccharomyces pombe attach centromeres to microtubules. Importantly, DASH complex proteins are conserved in many pathogenic fungi and lack homologs in metazoans. In S. cerevisiae, DASH complex members are essential for growth and may be promising drug targets. This proposal addresses the localization of DASH complex members in C. albicans, the interactions between DASH complex members and other kinetochore proteins, and the essentiality of DASH complex members for C. albicans growth. In addition, this project will test the hypothesis that the inverted repeat DNA sequences found in some C. albicans CEN regions contribute to the development of segmental aneuploidies and thus to the acquisition of drug resistance. Together, the proposed experiments will characterize the DASH complex proteins as potential antifungal drug targets and gain insight into the mechanism of segmental aneuploidy formation, a process that is correlated with the development of resistance to fluconazole. PUBLIC HEALTH RELEVANCE: Resistance of Candida albicans, the most commonly isolated human fungal pathogen, to anti- fungal drugs used during treatment is a significant problem. This proposal will examine several proteins associated with the C. albicans centromere to characterize their potential as anti-fungal drug targets. Also, this project will gain insight into the mechanism of how specific chromosomal rearrangments that result in resistance to a commonly used anti-fungal drug arise.